Regioselective N-2 arylation of indazoles

ABSTRACT

A novel process is provided for the efficient preparation of an asymmetric compound of structural formula I: 
                         
comprising a copper-catalyzed, carbon-nitrogen cross-coupling step. The process described as part of the present invention can be used to manufacture poly (ADP-ribose) polymerase (PARP) inhibitors, which may be useful for the treatment of cancer. In particular, the present invention describes a process for the manufacture of the PARP inhibitor, 2-{4-[(3S)-piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/419,618, filed on Jan. 30, 2017, which is a continuation of U.S.application Ser. No. 14/649,299, filed on Jun. 3, 2015, now U.S. Pat.No. 9,580,407, which is a U.S. National Phase application under 35U.S.A. § 371 of PCT Application No. PCT/US2013/072710, filed on Dec. 3,2013, which in turn claims the benefit of U.S. Provisional ApplicationNo. 61/734,392, filed on Dec. 7, 2012, all of which are herebyincorporated by reference in their entireties.

REFERENCE TO SEQUENCE LISTING

A sequence listing text file is submitted via EFS-Web in compliance with37 CFR § 1.52(e)(5) concurrently with the specification. The sequencelisting has the file name “23369-PCT-SEQTXT-15 Oct. 2013”, was createdon Oct. 15, 2013, and is 6,297 bytes in size. The sequence listing ispart of the specification and is incorporated in its entirety byreference herein.

BACKGROUND OF THE INVENTION

This invention describes the synthesis of the poly (ADP-ribose)polymerase (PARP) inhibitor,2-{4-[(3S)-Piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide, comprisingan optimized copper-catalyzed carbon-nitrogen coupling process utilizinga protecting group strategy. A crucial step in the synthesis of2-{4-[(3S)-Piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide includescoupling of a key piperidine intermediate with N-2 of a key indazoleintermediate. Protecting a primary amide of the parent indazole used inthe cross-coupling reaction results in a more efficient process withimproved reactivity and regioselective N-2 arylation.

Buchwald et al. (U.S. Pat. No. 6,235,936) describes methods for themetal-catalyzed arylation of hydrazines, hydrazones, hydroxylaminesand/or oximes through the formation of a carbon-heteroatom bond betweenan aromatic compound comprising an activated carbon bearing a leavinggroup and a heteroatom of a hydrazine, hydrazone, hydroxylamine oroxime.

PCT International Appl. No. PCT/US02/12785 (published WO 2002085838)describes copper-catalyzed methods for forming carbon-carbon andcarbon-heteroatom bonds.

U.S. Pat. No. 8,071,623 describes PARP inhibitors, including2-{4-[(3S)-Piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide and asynthesis of this compound.

Wallace et al. (2011, Organic Process Research and Development15:831-840) describes large-scale synthesis (up to 5 kg) routes of2-{4-[(3S)-Piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide relying oneither classical resolution or chiral separation.

SUMMARY OF THE INVENTION

The present invention relates to a method for the preparation of acompound of formula I:

wherein R² is hydrogen or an amine protecting group, comprisingcopper-catalyzed carbon-nitrogen cross-coupling of a piperidine compoundand an indazole intermediate. The process described as part of thepresent invention can be used to manufacture poly (ADP-ribose)polymerase (PARP) inhibitors disclosed in U.S. Pat. No. 8,071,623, whichmay be useful for the treatment of cancer. In particular, the presentinvention describes a process for the manufacture of the PARP inhibitor,2-{4-[(3S)-Piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an efficient process for the preparationa compound of formula I:

wherein R² is hydrogen or an amine protecting group, comprising:

(a) carbon-nitrogen cross-coupling of (i) an indazole of formula IIcontaining a protected amide:

wherein R¹ is C₁₋₈ alkyl, C₃₋₈ cycloalkyl, C₄₋₈ heterocyclyl, aryl,heteroaryl or arylC₁₋₈alkyl, optionally substituted with one to threearyl, heteroaryl, C₃₋₈ cycloalkyl or OC₁₋₈ alkyl; and (ii) a piperidinecompound of formula III:

wherein R³ is a leaving group and R² is as provided above, in thepresence of a catalytic amount of a copper salt, a suitable ligand, abase, and a solvent, forming a compound of formula IV:

wherein R¹ and R² are as provided above; and,

(b) de-protecting the amide of the compound of formula IV.

In one embodiment of the process of the present invention, the coppersalt is a Cu(I) or Cu(II) salt. Examples of copper salts that can beused in the disclosed process CuI, CuCl, CuCl₂, CuBr, CuBr.S(CH₃)₂,CuBr₂, CuF₂, CuOAc, Cu(OAc)₂, Cu₂O, CuO, CuSO₄, Cu(OTf)₂, Cu(OMs)₂,Cu(OTs)₂, Cu(NO₃)₂, Cu(BF₄)₂CuBr and (nBu₄-N)₂(CuI₂)₂ (Maligres, P. E.et al., 2012, J. Org. Chem. 77:7646-7651). In a further embodiment, thecopper salt is CuBr. In another embodiment, the copper salt is CuI.

The copper salt used in the process of the present invention is presentin an amount suitable to achieve efficient catalysis. The copper salt istypically present in an amount of 1-20 mol %. In one embodiment, thecopper salt is present in an amount less than or equal to about 10 mol %relative to the piperidine compound (e.g., a compound of formula III orthe compound of formula VIII, infra). In another embodiment, the coppersalt is present in an amount less than or equal to about 5 mol %relative to the piperidine compound. In a further embodiment, the coppersalt is present in an amount less than or equal to about 1 mol %relative to the piperidine compound. In one embodiment, the copper saltused in the present invention is CuBr and is present in an amount lessthan or equal to about 5 mol % relative to the piperidine compound. Inanother embodiment, the copper salt is CuBr and is present in an amountof about 5 mol % relative to the piperidine compound. In anotherembodiment, the copper salt used in the present invention is CuI and ispresent in an amount less than or equal to about 10 mol % relative tothe piperidine compound. In a further embodiment, the copper salt is CuIand is present in an amount of about 7.5 mol % relative to thepiperidine.

In one embodiment, R¹ is C₁₋₈ alkyl, C₃₋₈ cycloalkyl, C₄₋₈ heterocyclyl,aryl, heteroaryl or arylC₁₋₃alkyl, optionally substituted with one tothree phenyl (“Ph”), C₃ cycloalkyl or methoxy. In a further embodiment,R¹ is:

In a further embodiment, R¹ is:

In another embodiment, R¹ is tert-butyl, cumyl (—C(CH₃)₂Ph) or trityl(—C(Ph)₃). In a still further embodiment, R¹ is tert-butyl.

In one embodiment of the invention, R² is an amine protecting group.Examples of amine protecting groups that can be used are formyl, acetyl,trifluoroacetyl, benzyl, benzoyl, carbamate, benzyloxycarbonyl,p-methoxybenzyl carbonyl, tert-butoxycarbonyl, trimethylsilyl,2-trimethylsilyl-ethanesulfonyl, trityl and substituted trityl groups,allyloxycarbonyl, 9-fluorenylmethyloxycarbonyl,nitro-veratryloxycarbonyl, p-methoxybenzyl and tosyl. In a furtherembodiment, R² is the amine protecting group tert-butoxycarbonyl(“Boc”).

In one embodiment, R³ is Br or I. In a further embodiment, R³ is Br.

If R² is an amine protecting group, including but not limited totert-butoxycarbonyl (“Boc”), the process of the present invention mayfurther comprise a step wherein the piperidyl nitrogen of the compoundof formula IV is deprotected, forming the compound of formula V:

De-protection of the piperidyl nitrogen of the compound of formula IVmay occur at the same time (i.e., during the same reaction) as thede-protection of the amide of that compound.

Thus, in one embodiment, the present invention provides an efficientprocess for the preparation a compound of formula V:

comprising:

(a) carbon-nitrogen cross-coupling of (i) an indazole of formula IIcontaining a protected amide:

wherein R¹ is C₁₋₈ alkyl, C₃₋₁₀ cycloalkyl, C₄₋₁₀ heterocyclyl, aryl, orheteroaryl, and wherein said alkyl group is optionally substituted withone to three aryl or heteroaryl; and (ii) a piperidine compound offormula III:

wherein R³ is a leaving group and R² is an amine protecting group; inthe presence of a catalytic amount of a copper salt, a suitable ligand,a base, and a solvent, forming a compound of formula IV:

wherein R¹ and R² are as provided above; and,

(b) de-protecting both the amide and the piperidyl nitrogen of thecompound of formula IV, forming the compound of formula V.

The de-protecting step of part (b) can occur in a one-step or two-stepprocess. For example, in one embodiment, deprotection of the amide anddeprotection of the piperidyl nitrogen occur in single reaction (i.e.,one-step process). In another embodiment, the amide is de-protectedfirst (in one reaction), followed by de-protection of the piperidylnitrogen (in a separate reaction). In a further embodiment, thepiperidyl nitrogen is de-protected first, followed by deprotection notthe amide.

In another embodiment of a process of the invention, R¹ is tert-butyl,R² is tert-butoxycarbonyl, and R³ is Br.

The present invention further relates to a process for preparing acompound of formula VI:

comprising:

(a) carbon-nitrogen cross-coupling of (i) the indazole of formula VIIand (ii) the piperidine compound of formula VIII, wherein Boc istert-butoxycarbonyl:

in the presence of a catalytic amount of a copper salt, a suitableligand, a base, and a solvent, forming the compound of formula IX:

and,

(c) de-protecting both the amide and the piperidyl nitrogen of thecompound of formula IX in the presence of p-TsOH (aq), forming thecompound of formula VI.

The de-protecting step of part (c) can occur in a one-step or two-stepprocess. For example, in one embodiment, deprotection of the amide anddeprotection of the piperidyl nitrogen occur in single reaction (i.e.,one-step process). In another embodiment, the amide is de-protectedfirst (in one reaction), followed by de-protection of the piperidylnitrogen (in a separate reaction). In a further embodiment, thepiperidyl nitrogen is de-protected first, followed by deprotection nofthe amide.

In an embodiment of a process of the invention, the ligand present inthe carbon-nitrogen coupling reaction is selected from dimethylglycine,8-hydroxyquinoline, phenanthroline, neocuproine,3,4,7,8-tetramethyl-1,10-phenanthroline,2,2,6,6-tetramethyl-3,5-heptanedione, 2,6-dimethyl-3,5-heptanedione,2-isobutyrylcyclohexanone, 2-acetylcyclohexanone, 2,4-pentanedione,3,5-heptanedione, and N,N′-dimethylcyclohexane-1,2-diamine. In a furtherembodiment, the ligand is selected from dimethylglycine,8-hydroxyquinoline and N,N′-dimethylcyclohexane-1,2-diamine. In a stillfurther embodiment, the ligand is 8-hydroxyquinoline. In anotherembodiment, the ligand is N,N′-dimethylcyclohexane-1,2-diamine. In oneembodiment, the ligand is present in an amount less than or equal toabout 40 mol % relative to the piperidine intermediate (i.e., a compoundof formula III of the compound of formula VIII). In a furtherembodiment, the ligand is present in an amount less than or equal toabout 30 mol % relative to the piperidine intermediate. In anotherembodiment, the ligand is present in an amount less than or equal toabout 20 mol % relative to the piperidine intermediate. In a stillfurther embodiment, the ligand is present in an amount less than orequal to about 10 mol % relative to the piperidine intermediate.

In a further embodiment of the invention, the base present in thecarbon-nitrogen coupling step is a carbonate, phosphate, oxide,hydroxide, alkoxide, aryloxide, amine, metal amide, fluoride, orguanidine. In certain embodiments, the base is selected from K₂CO₃,K₃PO₄, K₂HPO₄, Cs₂CO₃, KHCO₃, Na₂CO₃ or NaHCO₃, or mixtures thereof. Inanother embodiment, the base is K₂CO₃. In a further embodiment, the baseis K₃PO₄. Typically, there is no need to use large excesses of base inthe process of the present invention. In certain embodiments, no morethan four equivalents of base are used, relative to the piperidinereactant. In other embodiments, no more than two equivalents of base areused, relative to the piperidine reactant

In one embodiment, the solvent present in the carbon-nitrogen couplingreaction is selected from dimethyl sulfoxide (DMSO), dimethylformamide(DMF), dimethylacetamide (DMAc), 1,3-dimethyl-2-imidazolidinone (DMI),N-methyl-2-pyrrolidone (NMP), sulfolane, pyridine, 2-picoline,3-picoline, 4-picoline, toluene, o-xylene, m-xylene, p-xylene, dioxane,chlorobenzene, anisole and any combinations thereof. In a furtherembodiment, the solvent is selected from dimethyl sulfoxide (DMSO),dimethylacetamide (DMAc) and toluene. In a still further embodiment, thesolvent is dimethylacetamide (DMAc). In another embodiment, the solventis toluene. In one embodiment, the solvent is present in thecarbon-nitrogen coupling reaction within a range of between about 0.09and about 1.4M.

The carbon-nitrogen coupling reaction may be performed at a temperatureof between about 90° C. and 130° C. In one embodiment, thecarbon-nitrogen coupling reaction is performed at a temperature of about100° C. In another embodiment, the reaction is performed at atemperature of about 110° C.

In one embodiment of a process of the invention, the carbon-nitrogencoupling reaction is performed in the presence of CuBr, the ligand8-hydroxyquinoline, the base K₂CO₃, and the solvent dimethylacetamide(DMAc), at a temperature of about 110° C. In a further embodiment, CuBris present in an amount of about 5 mol % relative to the piperidineintermediate (i.e., a compound of formula III or the compound of formulaVIII). In another embodiment, 8-hydroxyquinoline is present in an amountof about 10 mol % relative to the piperidine intermediate (i.e., acompound of formula III or the compound of formula VIII).

An indazole of formula II, used in the carbon-nitrogen coupling reactionstep of the disclosed process, may be formed by reactingindazole-7-carboxylic acid

with an amine in the presence of an organic reagent used to convertcarboxylic acids into amides (e.g., 1,1′-carbonyldiimidazole (CDI),O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluroniumhexafluorophosphate (HATU), etc.). The amine used in the reactiondepends on the R¹ substituent group of the specific formula II indazoleto be synthesized. For example, to make an indazole of formula VII,containing a tert-butyl group on the amide, tert-butylamine is used inthe reaction. To make an indazole of formula II containing a cumyl groupon the amide, cumylamine is used in the reaction. Likewise, to make anindazole of formula II containing a trityl group on the amide,tritylamine is used in the reaction.

Thus, a process of the present invention further comprises a step, priorto the carbon-nitrogen coupling step, wherein the indazole of formula IIis first synthesized, wherein R¹ of the indazole of formula II is R¹ isC₁₋₈ alkyl, C₃₋₈ cycloalkyl, C₄₋₈ heterocyclyl, aryl, heteroaryl orarylC₁₋₈alkyl, optionally substituted with one to three aryl,heteroaryl, C₃₋₈ cycloalkyl or OC₁₋₈ alkyl, by reactingindazole-7-carboxylic acid with an amine, including but not limited totert-butylamine, cumylamine and tritylamine, and an organic chemicalcapable of converting a carboxylic acid into an amide. In oneembodiment, the indazole of formula VIII is synthesized by reactingindazole-7-carboxylic acid with tert-butylamine in the presence of CDI.In another embodiment, an indazole of formula II, where R¹ is cumyl(—C(CH₃)₂Ph), is synthesized by reacting indazole-7-carboxylic acid withcumylamine in the presence of HATU. In a further embodiment, an indazoleof formula II, where R¹ is trityl (—C(Ph)₃), is synthesized by reactingindazole-7-carboxylic acid with triphenylmethyl amine in the presence ofHATU. In another embodiment, an indazole of formula II, where R¹ is abenzyl group, is synthesized by reacting indazole-7-carboxylic acid withbenzyl amine in the presence of HATU. In a still further embodiment, anindazole of formula II, where R¹ is a 2,4-dimethyloxybenzyl group, issynthesized by reacting indazole-7-carboxylic acid with2,4-dimethyoxybenzyl amine in the presence of HATU. In anotherembodiment, an indazole of formula II, where R¹ is an alpha-methylbenzyl group, is synthesized by reacting indazole-7-carboxylic acid withalpha-methylbenzyl amine in the presence of HATU

The piperidine compounds used in the carbon-nitrogen coupling reactionstep of the disclosed process (i.e., compounds of formula III andformula VIII) may be formed by employing dynamic kinetic resolution(DKR) involving an enzymatic enantioselective amination reactioncatalyzed by a transaminase. Methods of preparing such piperidinecompounds are specifically described in co-filed provisional applicationentitled “Biocatalytic Transamination Process,” U.S. Provisional ApplNo. 61/734,394, incorporated by reference herein. For example, theasymmetric piperidine compound of formula VIII can be prepared by aprocess comprising:

(a) biocatalytic transamination of a compound of formula X or a compoundof formula XI:

in the presence of a transaminase polypeptide, a coenzyme, and an aminodonor, forming the compound of formula XII:

(b) reducing the lactam of the compound of Formula XII, forming thecompound of Formula XIII:

and,

(c) protecting the piperidine nitrogen of the compound of Formula XIIIto form the compound of formula VIII.

Thus, a process of the present invention further comprises a step, priorto the carbon-nitrogen coupling step, wherein a piperidine compound offormula III or formula VIII is first synthesized by employing dynamickinetic resolution (DKR) involving an enzymatic enantioselectiveamination reaction catalyzed by a transaminase. In one embodiment, thetransaminase polypeptide is a naturally occurring transaminase. Inanother embodiment, the transaminase polypeptide is a synthetic variantof a naturally occurring transaminase. In a further embodiment, thetransaminase polypeptide is selected from SEQ ID NO: 1 or SEQ ID NO: 2.In a further embodiment, the transaminase polypeptide is SEQ ID NO: 2.In another embodiment, isopropylamine is used as an amino donor. In afurther embodiment, pyridoxal-phosphate is used as a coenzyme.

Definitions

For convenience, certain terms employed in the specification, examples,and appended claims are collected here.

“Amino donor” or “amine donor” refers to an amino compound which donatesan amino group to an amino acceptor, thereby becoming a carbonylspecies. Amino donors are molecules of general formula shown below,

in which each of R^(3*), R^(4*), when taken independently, is an alkyl,an alkylaryl group, or aryl group which is unsubstituted or substitutedwith one or more enzymatically non-inhibiting groups. R^(3*) can be thesame or different from R^(4*) in structure or chirality. R^(3*) andR^(4*), taken together, may form a ring that is unsubstituted,substituted, or fused to other rings. Typical amino donors includechiral and achiral amino acids, and chiral and achiral amines.

“Chiral amine” refers to amines of general formula R^(α)—CH(NH₂)—R^(β)and is employed herein in its broadest sense, including a wide varietyof aliphatic and alicyclic compounds of different, and mixed, functionaltypes, characterized by the presence of a primary amino group bound to asecondary carbon atom which, in addition to a hydrogen atom, carrieseither (i) a divalent group forming a chiral cyclic structure, or (ii)two substituents (other than hydrogen) differing from each other instructure or chirality. Divalent groups forming a chiral cyclicstructure include, for example, 2-methylbutane-1,4-diyl,pentane-1,4-diyl, hexane-1,4-diyl, hexane-1,5-diyl,2-methylpentane-1,5-diyl. The two different substituents on thesecondary carbon atom (R^(α) and R^(β) above) also can vary widely andinclude alkyl, arylalkyl, aryl, halo, hydroxy, lower alkyl, loweralkyloxy, lower alkylthio, cycloalkyl, carboxy, carbalkyloxy, carbamoyl,mono- and di-(lower alkyl) substituted carbamoyl, trifluoromethyl,phenyl, nitro, amino, mono- and di-(lower alkyl) substituted amino,alkylsulfonyl, arylsulfonyl, alkylcarboxamido, arylcarboxamido, etc., aswell as alkyl, arylalkyl, or aryl substituted by the foregoing.

Exemplary amino donors include isopropylamine (also referred to as2-aminopropane or “IPM”), α-phenethylamine (also termed1-phenylethanamine), and its enantiomers (S)-1-phenylethanamine and(R)-1-phenylethanamine, 2-amino-4-phenylbutane, glycine, L-glutamicacid, L-glutamate, monosodium glutamate, L-alanine, D-alanine,D,L-alanine, L-aspartic acid, L-lysine, D,L-ornithine, β-alanine,taurine, n-octylamine, cyclohexylamine, 1,4-butanediamine (also referredto as putrescine), 1,6-hexanediamine, 6-aminohexanoic acid,4-aminobutyric acid, tyramine, and benzyl amine, 2-aminobutane,2-amino-1-butanol, 1-amino-1-phenylethane,1-amino-1-(2-methoxy-5-fluorophenyl)ethane, 1-amino-1-phenylpropane,1-amino-1-(4-hydroxyphenyl)propane, 1-amino-1-(4-bromophenyl)propane,1-amino-1-(4-nitrophenyl)propane, 1-phenyl-2-aminopropane,1-(3-trifluoromethylphenyl)-2-aminopropane, 2-aminopropanol,1-amino-1-phenylbutane, 1-phenyl-2-aminobutane,1-(2,5-dimethoxy-4-methylphenyl)-2-aminobutane, 1-phenyl-3-aminobutane,1-(4-hydroxyphenyl)-3-aminobutane, 1-amino-2-methylcyclopentane,1-amino-3-methylcyclopentane, 1-amino-2-methylcyclohexane,1-amino-1-(2-naphthyl)ethane, 3-methylcyclopentylamine,2-methylcyclopentylamine, 2-ethylcyclopentylamine,2-methylcyclohexylamine, 3-methylcyclohexylamine, 1-aminotetralin,2-aminotetralin, 2-amino-5-methoxytetralin, and 1-aminoindan, includingboth (R) and (S) single isomers where possible and including allpossible salts of the amines.

“Amino acceptor” and “amine acceptor,” “keto substrate,” “keto,” and“ketone” are used interchangeably herein to refer to a carbonyl (keto,or ketone) compound which accepts an amino group from a donor amine.Amino acceptors are molecules of general formula shown below,

in which each of R^(1*), R^(2*), when taken independently, is an alkyl,an alkylaryl group, or aryl group which is unsubstituted or substitutedwith one or more enzymatically acceptable groups. R^(1*) may be the sameor different from R^(2*) in structure or chirality. In some embodiments,R^(1*) and R^(2*), taken together, may form a ring that isunsubstituted, substituted, or fused to other rings. Amino acceptorsinclude keto carboxylic acids, alkanones (ketones), and alkanals(aldehydes).

“Coenzyme,” as used herein, refers to a non-protein compound thatoperates in combination with an enzyme in catalyzing a reaction. As usedherein, “coenzyme” is intended to encompass the vitamin B₆ familycompounds, PLP, PN, PL, PM, PNP and PMP.

“Pyridoxal-phosphate,” “PLP,” “pyridoxal-5′-phosphate,” “PYP,” and “P5P”are used interchangeably to refer to a compound that acts as a coenzymein transaminase reactions. In some embodiments, pyridoxal phosphate isdefined by the structure1-(4′-formyl-3′-hydroxy-2′-methyl-5′-pyridyl)methoxyphosphonic acid, CASnumber [54-47-7]. Pyridoxal-5′-phosphate can be produced in vivo byphosphorylation and oxidation of pyridoxol (also known as Vitamin B₆).In transamination reactions using transaminase enzymes, the amine groupof the amino donor is transferred to the coenzyme to produce a ketoby-product, while pyridoxal-5′-phosphate is converted to pyridoxaminephosphate. Pyridoxal-5′-phosphate is regenerated by reaction with adifferent keto compound (the amino acceptor). The transfer of the aminegroup from pyridoxamine phosphate to the amino acceptor produces anamine and regenerates the coenzyme. In some embodiments, thepyridoxal-5′-phosphate can be replaced by other members of the vitaminB₆ family, including pyridoxine (PN), pyridoxal (PL), pyridoxamine (PM),and their phosphorylated counterparts; pyridoxine phosphate (PNP), andpyridoxamine phosphate (PMP).

“Leaving group” is defined as a term that would be understood by one ofordinary skill in the art; that is, a group on a carbon where, uponreaction, a new bond is to be formed and the carbon loses the group uponformation of the new bond. A typical example employing a suitableleaving group is a nucleophilic substitution reaction, e.g., on a sp³hybridized carbon (S_(N)2 or S_(N)1), e.g. where the leaving group is ahalide, such as a bromide, and the reactant might be benzyl bromide.Another typical example of such a reaction is a nucleophilic aromaticsubstitution reaction (SNAr). Another example is an insertion reaction(for example by a transition metal) into the bond between an aromaticreaction partner bearing a leaving group followed by reductive coupling.“Leaving group” is not limited to such mechanistic restrictions.Examples of suitable leaving groups include halogens (fluorine,chlorine, bromine or iodine), optionally substituted aryl or alkylsulfonates, phosphonates, azides and —S(O)₀₋₂R where R is, for example,optionally substituted alkyl, optionally substituted aryl, or optionallysubstituted heteroaryl. Those of skill in the art of organic synthesiswill readily identify suitable leaving groups to perform a desiredreaction under different reaction conditions. Non-limitingcharacteristics and examples of leaving groups can be found, for examplein Organic Chemistry, 2nd ed., Francis Carey (1992), pages 328-331;Introduction to Organic Chemistry, 2d ed., Andrew Streitwieser andClayton Heathcock (1981), pages 169-171; and Organic Chemistry, 5th Ed.,John McMurry, Brooks/Cole Publishing (2000), pages 398 and 408; all ofwhich are incorporated herein by reference.

“Protecting group” refers to a group of atoms that mask, reduce orprevent the reactivity of the functional group when attached to areactive functional group in a molecule. Typically, a protecting groupmay be selectively removed as desired during the course of a synthesis.Examples of protecting groups can be found in Wuts and Greene, “Greene'sProtective Groups in Organic Synthesis,” 4^(th) Ed., Wiley Interscience(2006), and Harrison et al., Compendium of Synthetic Organic Methods,Vols. 1-8, 1971-1996, John Wiley & Sons, NY. Functional groups that canhave a protecting group include, but are not limited to, hydroxy, amino,and carboxy groups.

Representative amine protecting groups include, but are not limited to,formyl, acetyl (Ac), trifluoroacetyl, benzyl (Bn), benzoyl (Bz),carbamate, benzyloxycarbonyl (“CBZ”), p-methoxybenzyl carbonyl (Moz orMeOZ), tert-butoxycarbonyl (“Boc”), trimethylsilyl (“TMS”),2-trimethylsilyl-ethanesulfonyl (“SES”), trityl and substituted tritylgroups, allyloxycarbonyl, 9-fluorenylmethyloxycarbonyl (“FMOC”),nitro-veratryloxycarbonyl (“NVOC”), p-methoxybenzyl (PMB), tosyl (Ts)and the like.

As used herein except where noted, “alkyl” is intended to include bothbranched- and straight-chain saturated aliphatic hydrocarbon groupshaving the specified number of carbon atoms. For example, “C₁-C₈” or“C₁₋₈,” as in “C₁-C₈ alkyl” or “C₁₋₈ alkyl,” is defined to includegroups having 1, 2, 3, 4, 5, 6, 7 or 8 carbons in a linear or branchedarrangement. C₁₋₈ alkyl includes all of the hexyl alkyl and pentyl alkylisomers as well as n-, iso-, sec- and t-butyl, n- and isopropyl, ethyland methyl. As another example, C₁₋₄ alkyl means n-, iso-, sec- andt-butyl, n- and isopropyl, ethyl and methyl. As another example, C₁-C₁₀alkyl specifically includes methyl, ethyl, n-propyl, i-propyl, n-butyl,t-butyl, i-butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, and so on.If no number is specified, 1-10 carbon atoms are intended for linear orbranched alkyl groups. Commonly used abbreviations for alkyl groups areused throughout the specification, e.g. methyl may be represented byconventional abbreviations including “Me” or CH₃ or a symbol that is anextended bond without defined terminal group, e.g.

ethyl may be represented by “Et” or CH₂CH₃, propyl may be represented by“Pr” or CH₂CH₂CH₃, butyl may be represented by “Bu” or CH₂CH₂CH₂CH₃,etc. The term “cycloalkyl” means a monocyclic saturated aliphatichydrocarbon group having the specified number of carbon atoms. Forexample, “cycloalkyl” includes cyclopropyl, methyl-cyclopropyl,2,2-dimethyl-cyclobutyl, 2-ethyl-cyclopentyl, cyclohexyl, cyclopentenyl,cyclobutenyl and so on.

“Aryl,” unless otherwise indicated, is intended to mean any stablemonocyclic or bicyclic carbon ring of up to 7 atoms in each ring,wherein at least one ring is aromatic. Examples of such aryl elementsinclude phenyl, naphthyl, tetrahydronaphthyl, indanyl and biphenyl. Incases where the aryl substituent is bicyclic and one ring isnon-aromatic, it is understood that attachment is via the aromatic ring.In an embodiment, aryl is phenyl.

The term “heteroaryl,” as used herein, represents a stable monocyclic orbicyclic ring of up to 7 atoms in each ring, wherein at least one ringis aromatic and contains from 1 to 4 heteroatoms selected from the groupconsisting of O, N and S. Heteroaryl groups within the scope of thisdefinition include but are not limited to: acridinyl, carbazolyl,cinnolinyl, quinoxalinyl, pyrrazolyl, indolyl, benzotriazolyl, furanyl,thienyl, benzothienyl, benzofuranyl, benzimidazolonyl, benzoxazolonyl,quinolinyl, isoquinolinyl, dihydroisoindolonyl, imidazopyridinyl,isoindolonyl, indazolyl, oxazolyl, oxadiazolyl, isoxazolyl, indolyl,pyrazinyl, pyridazinyl, pyridinyl, pyrimidinyl, pyrrolyl,tetrahydroquinoline. As with the definition of heterocycle below,“heteroaryl” is also understood to include the N-oxide derivative of anynitrogen-containing heteroaryl. In cases where the heteroarylsubstituent is bicyclic and one ring is non-aromatic or contains noheteroatoms, it is understood that attachment is via the aromatic ringor via the heteroatom containing ring, respectively.

The term “heterocycle” or “heterocyclyl,” as used herein, is intended tomean a 3- to 10-membered aromatic or nonaromatic heterocycle containingfrom 1 to 4 heteroatoms selected from the group consisting of O, N andS, and includes bicyclic groups. For the purposes of this invention, theterm “heterocyclic” is also considered to be synonymous with the terms“heterocycle” and “heterocyclyl” and is understood as also having thedefinitions set forth herein. “Heterocyclyl” therefore includes theabove mentioned heteroaryls, as well as dihydro and tetrahydro analogsthereof. Further examples of “heterocyclyl” include, but are not limitedto the following: azetidinyl, benzoimidazolyl, benzofuranyl,benzofurazanyl, benzopyrazolyl, benzotriazolyl, benzothiophenyl,benzoxazolyl, carbazolyl, carbolinyl, cinnolinyl, furanyl, imidazolyl,indolinyl, indolyl, indolazinyl, indazolyl, isobenzofuranyl, isoindolyl,isoquinolyl, isothiazolyl, isoxazolyl, naphthpyridinyl, oxadiazolyl,oxooxazolidinyl, oxazolyl, oxazoline, oxopiperazinyl, oxopyrrolidinyl,oxomorpholinyl, isoxazoline, oxetanyl, pyranyl, pyrazinyl, pyrazolyl,pyridazinyl, pyridopyridinyl, pyridazinyl, pyridyl, pyrimidyl, pyrrolyl,quinazolinyl, quinolyl, quinoxalinyl, tetrahydropyranyl,tetrahydrofuranyl, tetrahydrothiopyranyl, tetrahydroisoquinolinyl,tetrazolyl, tetrazolopyridyl, thiadiazolyl, thiazolyl, thienyl,triazolyl, 1,4-dioxanyl, hexahydroazepinyl, piperazinyl, piperidinyl,pyridin-2-onyl, pyrrolidinyl, morpholinyl, thiomorpholinyl,dihydrobenzoimidazolyl, dihydrobenzofuranyl, dihydrobenzothiophenyl,dihydrobenzoxazolyl, dihydrofuranyl, dihydroimidazolyl, dihydroindolyl,dihydroisooxazolyl, dihydroisothiazolyl, dihydrooxadiazolyl,dihydrooxazolyl, dihydropyrazinyl, dihydropyrazolyl, dihydropyridinyl,dihydropyrimidinyl, dihydropyrrolyl, dihydroquinolinyl,dihydrotetrazolyl, dihydrothiadiazolyl, dihydrothiazolyl,dihydrothienyl, dihydrotriazolyl, dihydroazetidinyl,dioxidothiomorpholinyl, methylenedioxybenzoyl, tetrahydrofuranyl, andtetrahydrothienyl, and N-oxides thereof. Attachment of a heterocyclylsubstituent can occur via a carbon atom or via a heteroatom.

As used herein, the term “substituted” is contemplated to include allpermissible substituents of organic compounds. In a broad aspect, thepermissible substituents include acyclic and cyclic, branched andunbranched, carbocyclic and heterocyclic, aromatic and nonaromaticsubstituents of organic compounds. Illustrative substituents include,for example, those described hereinabove.

“Protein,” “polypeptide,” and “peptide” are used interchangeably hereinto denote a polymer of at least two amino acids covalently linked by anamide bond, regardless of length or post-translational modification(e.g., glycosylation, phosphorylation, lipidation, myristilation,ubiquitination, etc.). Included within this definition are D- andL-amino acids, and mixtures of D- and L-amino acids.

“Stereoselectivity” refers to the preferential formation in a chemicalor enzymatic reaction of one stereoisomer over another.Stereoselectivity can be partial, where the formation of onestereoisomer is favored over the other, or it may be complete where onlyone stereoisomer is formed. When the stereoisomers are enantiomers, thestereoselectivity is referred to as enantio selectivity, the fraction(typically reported as a percentage) of one enantiomer in the sum ofboth. It is commonly alternatively reported in the art (typically as apercentage) as the enantiomeric excess (e.e.) calculated there fromaccording to the formula [major enantiomer—minor enantiomer]/[majorenantiomer+minor enantiomer]. Where the stereoisomers arediastereoisomers, the stereoselectivity is referred to asdiastereoselectivity, the fraction (typically reported as a percentage)of one diastereomer in a mixture of two diastereomers, commonlyalternatively reported as the diastereomeric excess (d.e.). Where amixture contains more than two diastereomers it is common to report theratio of diastereomers or “diastereomeric ratio” rather thandiastereomeric excess. Enantiomeric excess and diastereomeric excess aretypes of stereomeric excess.

The term “regioisomers” refers to compounds which have the samemolecular formula but differ in the connectivity of the atoms.Accordingly, a regioselective process is one which favors the productionof a particular regioisomer over others, e.g., the reaction produces astatistically significant preponderance of a certain regioisomer. Aregioselective reaction is a reaction which occurs preferentially at onereactive center rather than another non-identical reactive center.

“Transaminase,” “transaminase polypeptide” and “transaminase enzyme,” asused interchangeably herein, refer to a polypeptide having an enzymaticcapability of transferring an amino group (NH₂), a pair of electrons,and a proton from a primary amine of an amino donor to a carbonyl group(C═O; i.e., a keto group) of an amino acceptor molecule. Transaminaseshave been identified from various organisms, such as Alcaligenesdenitrificans, Arthrobacter, Bordetella bronchiseptica, Bordetellaparapertussis, Brucella melitensis, Burkholderia malle, Burkholderiapseudomallei, Chromobacterium violaceum, Oceanicola granulosus HTCC2516,Oceanobacter sp. RED65, Oceanospirillum sp. MED92, Pseudomonas putida,Ralstonia solanacearum, Rhizobium meliloti, Rhizobium sp. (strainNGR234), Bacillus thuringensis, Vibrio fluvialis and Klebsiellapneumoniae (see, e.g., Shin et al., 2001, Biosci. Biotechnol. Biochem.65: 1782-1788). Both R-selective and S-selective transaminases areknown. The wild-type transaminase from Arthrobacter sp. KNK168 is anR-selective, pyridoxal 5′-phosphate (PLP)-dependent enzyme that producesR-amines from some substrates (see, e.g., Iwasaki et al., 2006, Appl.Microbiol. Biotechnol., 69:499-505; U.S. Pat. No. 7,169,592).Non-naturally occurring, engineered transaminase polypeptides generatedby human manipulation are available (see, e.g., U.S. application Ser.No. 12/714,397, published as US20100285541; PCT International Appl.serial no. PCT/US2010/025685, published as WO 2010/099501; PCTInternational Appl. serial no. PCT/US2011/046932, published as WO2012/024104).

“Naturally-occurring” or “wild-type” refers to the form found in nature.For example, a naturally occurring or wild-type polypeptide orpolynucleotide sequence is a sequence that can be isolated from a sourcein nature and which has not been intentionally modified by humanmanipulation.

Reaction Conditions

As described further below, and illustrated in the Examples, the presentprocess contemplates ranges of suitable reaction conditions that can beused in the copper-catalyzed carbon-nitrogen coupling and deprotectionprocesses disclosed, including but not limited to ranges of pH,temperature, buffer, solvent system, substrate loading, catalystloading, ligand loading, atmosphere, and reaction time. Further suitablereaction conditions for carrying out the process steps described hereincan be readily optimized by routine experimentation, including by usingthe methods described in the Examples provided herein; thus, it will beunderstood that the conditions and/or ranges recited herein are notlimitative and only correspond to a mode of the process of theinvention.

The term “catalytic amount” is recognized in the art and means asubstoichiometric amount relative to a reactant.

“Suitable reaction conditions” refers to those conditions in thereaction solution (e.g., ranges of catalyst and ligand, substrateloading, temperature, pH, buffers, solvents/co-solvents, etc.) underwhich a copper-catalyst system is capable of coupling an indazoleintermediate and a piperidine intermediate as described in detail above.

“Substrate,” in the context of the disclosed copper-catalyzedcarbon-nitrogen coupling process, refers to the intermediate(pre-coupled) compounds, e.g., the indazole and piperidine compoundsdisclosed herein.

In certain embodiments of the process, the temperature of the suitablereaction conditions can be chosen to maximize the reaction rate athigher temperatures while maintaining the activity of the catalysisreaction for efficient synthesis. In certain embodiments, thecarbon-nitrogen coupling reaction of the present invention is conductedat a temperature between about 90° C. and about 130° C. In oneembodiment, the carbon-nitrogen coupling reaction of the presentinvention is conducted at a temperature equal to or less than about 130°C. In certain embodiments, the carbon-nitrogen coupling reaction of thepresent invention is conducted at a temperature equal to or less thanabout 120° C. In certain embodiments, the carbon-nitrogen couplingreaction of the present invention is conducted at a temperature equal toor less than about 110° C. In certain embodiments, the carbon-nitrogencoupling reaction of the present invention is conducted at a temperatureequal to or less than about 100° C. In certain embodiments, thecarbon-nitrogen coupling reaction of the present invention is conductedat a temperature between about 100° C. to about 110° C. In certainembodiments, the carbon-nitrogen coupling reaction of the presentinvention is conducted at a temperature about 90° C. In certainembodiments, the carbon-nitrogen coupling reaction of the presentinvention is conducted at a temperature about 100° C. In certainembodiments, the carbon-nitrogen coupling reaction of the presentinvention is conducted at a temperature about 110° C.

In certain embodiments, the process steps of the present invention canbe carried out at the pH of the solution at the time of initial reactantmixing and may be maintained at a desired pH or within a desired pHrange by the addition of an acid or a base during the course of thereaction. In certain embodiments of the process, the pH of the reactionmixture may be allowed to change, or be changed during the course of thereaction. Alternatively, a buffer of buffering system may be used tomaintain the reaction at a desired pH. Suitable buffers to maintaindesired pH ranges are known in the art and include, for example,phosphate buffer, triethanolamine buffer, and the like. Combinations ofbuffering and acid or base addition may also be used.

The reaction processes of the present invention can be conducted incontinuous, semi-continuous or batch fashion and may involve a liquidrecycle operation as desired. The processes of this invention arepreferably conducted in batch fashion. Likewise, the manner or order ofaddition of the reaction ingredients, catalyst and solvent are notgenerally critical to the success of the reaction and may beaccomplished in any conventional fashion. The reactants may be addedtogether at the same time to a solvent, or alternatively, some of thereactants may be added separately, and some together at different timepoints. In certain embodiments, it is preferable to perform thereactions under an inert atmosphere of a gas such as nitrogen or argon.

The reaction can be conducted in a single reaction zone or in aplurality of reaction zones, in series or in parallel or it may beconducted batchwise or continuously in an elongated tubular zone orseries of such zones. The materials of construction employed should beinert to the starting materials during the reaction and the fabricationof the equipment should be able to withstand the reaction temperaturesand pressures. Means to introduce and/or adjust the quantity of startingmaterials or ingredients introduced batchwise or continuously into thereaction zone during the course of the reaction can be convenientlyutilized in the processes especially to maintain the desired molar ratioof the starting materials. The reaction steps may be affected by theincremental addition of one of the starting materials to the other.Also, the reaction steps can be combined by the joint addition of thestarting materials to the copper catalyst. When complete conversion isnot desired or not obtainable, the starting materials can be separatedfrom the product and then recycled back into the reaction zone.

The processes may be conducted in either glass-lined, stainless steel orsimilar type reaction equipment. The reaction zone may be fitted withone or more internal and/or external heat exchanger(s) in order tocontrol undue temperature fluctuations, or to prevent any possible“runaway” reaction temperatures. Furthermore, one or more of thereactants or the catalyst can be immobilized by attachment to orincorporation into a polymer or other insoluble matrix

The quantities of reactants used in the process steps of the presentinvention reaction will generally vary depending on the quantities ofproduct desired, and concomitantly the amount of catalyst and substratesemployed. Those having ordinary skill in the art will readily understandhow to vary these quantities to tailor them to the desired level ofproductivity and scale of production. Transformation of substrates toproduct can be monitored using known methods by detecting substrateand/or product. Suitable methods include gas chromatography, HPLC, andthe like.

These and other aspects of the invention will be apparent from theteachings contained herein.

EXAMPLES

Examples provided are intended to assist in a further understanding ofthe invention. Particular materials employed, species and conditions areintended to be illustrative of the invention and not limiting of thereasonable scope thereof.

Certain starting materials and reagents are either commerciallyavailable or known in the chemical scientific or patent literature.Purification procedures include, for example, distillation,crystallization, and normal or reverse phase high performance liquidchromatography.

The abbreviations used herein have the following tabulated meanings (seeTable 1). Abbreviations not tabulated below have their meanings ascommonly used unless specifically stated otherwise.

TABLE 1 MTBE = Methyl-tert-butyl ether NaOH = Sodium hydroxide AlCl₃ =Aluminum chloride H₂SO₄ = Sulfuric acid IPA = Isopropyl alcohol Na₂CO₃ =Sodium carbonate MgSO₄ = Magnesium sulfate Me₃SOI = Trimethylsulfoxonium iodide KOt-Bu_((s)) = Potassium tert-butoxide DMSO =Dimethyl sulfoxide THF = Tetrahydrofuran Na₂SO₄ = Sodium sulfate ZnBr₂ =Zinc bromide NaHSO₃ = Sodium bisulfite PhMe = Toluene NaCl = Sodiumchloride iPrNH₂ = Isopropylamine MeCN = Acetonitrile PLP =Pyridoxal-phosphate NaBH₄ = Sodium borohydride EtOH = Ethanol BF₃•THF =Boron trifluoride tetrahydrofuran complex MeOH = Methanol NH₄OH =Ammonium hydroxide LCAP = Liquid chromatography area percent p-TsOH =p-Toluenesulfonic acid (BOC)₂O = Di-tert-butyl dicarbonate DMAc =Dimethylacetamide DMF = Dimethylformamide CDI = 1,1′-Carbonyldiimidazolet-BuNH₂ tert-butylamine CuBr = Copper bromide MSA = Methanesulfonic acidDIPEA = Diisopropylethylamine

Example 1

The following Example 1 describes synthesis of the compound2-{4-[(3S)-Piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide:

1.1 Acylation

A mixture of succinic anhydride 1 (110 g) and bromobenzene (695 mL) wascooled to below 5° C. then added AlCl₃ (294 g). The slurry was allowedto warm to RT and then aged until the reaction was complete judged byHPLC. The reaction mixture was then transferred slowly into a cold HClsolution resulting in the formation of a white precipitate. The whiteslurry was filtered through a fritted funnel rinsing with H₂O. To theoff-white product was added MTBE and extracted with aq. NaOH. Theaqueous layer was cooled in an ice bath. Concentrated HCl was added dropwise to adjust the solution pH to 1, resulting in the formation of awhite slurry. The slurry was collected on a fritted funnel, rinsed withH₂O, and dried under vacuum with a N₂ sweep at RT to give the targetcompound (265 g, 93% corrected yield) as a white powder.

1.2 Esterification

A mixture of the acid 2 (205 g), IPA (4 L) and conc. H₂SO₄ (2.13 mL/3.91g) was heated to a gentle reflux until the reaction was complete judgedby HPLC. The solution was then cooled to RT and concentrated to a volumeof 350-400 mL. The residue was dissolved in MTBE (1.2 L), washed withaq. Na₂CO₃ followed by water. After dried over MgSO₄, the filtrate wassolvent-switched into heptane. The slurry was then filtered, and thecake was washed with cold heptane. After drying under vacuum, the targetcompound (223.5 g, 93% corrected yield) was obtained as a white powder.

1.3 Epoxidation

A mixture of Me₃SOI (230 g) and DMSO (300 mL) was added KOt-Bu (113 g)followed by DMSO (300 mL). The mixture was aged for a further 1.5 hr. Ina separate flask, ketone 3 (230 g) was dissolved in a mixture of THF(250 mL) and DMSO (150 mL), and the resulting solution was added dropwise to the ylide solution. The mixture was aged for 2 hr at RT, addedhexanes (1 L), and then quenched by the addition of ice-water (600 mL).The layers were cut, and the organic layer was washed with water thenwith brine. The slightly cloudy yellow organic layer was dried overNa₂SO₄ and filtered through a fritted funnel. Product solution assay was176.1 g (76% assay yield). This solution was carried forward into therearrangement step.

1.4 Epoxide Rearrangement and Bisulfite Formation

A solution of crude epoxide 4 (assay 59.5 g) in hexanes was solventswitched into PhMe, and added ZnBr₂ (10.7 g). When the rearrangement wascomplete judged by HPLC, the slurry was filtered through a frittedfunnel. The clear filtrate was washed with 10% aq. NaCl and then stirredwith a solution of sodium bisulfite (NaHSO₃, 24.7 g) in H₂O (140 mL)vigorously at RT for 3 hr. The cloudy aqueous layer was separated andwashed with heptanes. By ¹H-NMR assay, the aqueous solution contained71.15 g bisulfite adduct 6 (30.4 wt % solution, 90% yield from crudeepoxide 4). This solution was used directly in the subsequenttransaminase step.

1.5 Transaminase DKR

To a cylindrical Labfors reactor was charged pyridoxal-5-phosphate (1.4g, 5.66 mmol), 452 ml 0.2 M borate buffer pH 10.5 containing 1M iPrNH₂,52 g transaminase (SEQ ID NO: 180), and 75 ml DMSO, and the resultingmixture was warmed to 45° C. The pH was controlled at pH 10.5 using 8 Maq iPrNH₂. To this was added dropwise a mixture of 17.16 wt % aqsolution of ester bi-sulfite 6 (147.2 g, 353 mmol) and 219 ml DMSO underN₂ atmosphere. When the reaction was complete judged by HPLC, thereaction mixture was cooled and extracted with 1 volume of 3:2 IPA:IPAc.The aq/rag layer was extracted again with 1 volume of 3:7 IPA:IPAc. Theorganic layer was washed with brine at pH>9. Assay yield in solution was78 g (87%); 99.3% ee. After dried over MgSO₄, and filtered through afritted funnel, the crude solution was concentrated under vacuumflushing with IPAc to remove IPA. The resulting slurry was concentratedto a final volume of ˜200 mL, cool to below 0° C., and filtered tocollect the solid. The cake was washed with ice-cold IPAc and dried atRT under vacuum to give the desired product (84% corrected yield, 99.3LCAP) as a white powder.

1.6 Reduction of Amide

The lactam 7 can be reduced to form the piperidine 8 as described below:

A mixture of lactam 7 (10.25 g at 97.5 wt %) in THF (100 mL) was cooledto <10° C., and added NaBH₄ (4.47 g). EtOH (6.89 mL) was then addedslowly over 20 min. The slurry was aged for an additional 1 hr at 2° C.after which BF₃.THF (13.03 mL) was added over 1 hr. The slurry wasslowly warmed to RT and aged until complete conversion judged by HPLC.The reaction was then cooled to <5° C. then slowly quenched with MeOH(7.96 mL), added HCl (9.69 mL), then the reaction was heated to 45° C.until decomplexation of product-borane complex was complete, asindicated by LC assay. The reaction was cooled, diluted with IPAc (75mL) and water (80 mL), and then pH was adjusted with aqueous NH₄OH to pH8. The organic layer was separated, added 75 mL water, then pH adjustedto 10.5 with 50 wt % NaOH. The layers were separated and the organiclayer was washed with brine. After solvent-switched to IPAc, LC Assayyield was 9.1 g; 95.9%.

1.7 Tosylate Salt Formation

The tosylate salt of the piperidine 8 can be formed as described below:

The crude piperidine 8 free base in IPA was heated to ˜40° C. TsOH.H₂Osolids was added portion-wise. The slurry was warmed to 50° C. and heldat that temperature for 2 h, and then slowly cooled to RT and agedovernight. Supernatant concentration was measured to be 2.5 g/ml (freebase concentration). The solids were filtered and washed with IPAc (3×15mL) and dried at RT. Isolated solides: 14.85 g, 96% corrected isolatedyield.

1.8 Boc Protection

The piperidine 8 tosylate salt can be protected as described below:

To a stirred slurry of the tosylate salt of piperidine 8 (25.03 g, 60.6mmol) in MTBE (375 ml) was added NaOH (aq. 1.0 N, 72.7 ml, 72.7 mmol) atRT. To the mixture, (BOC)₂O (13.36 ml, 57.6 mmol) was added slowly over3 min. The resulting mixture was stirred for 4.5 hr at RT, and then theaqueous layer was separated. The MTBE layer was washed with water (100ml×2). The organic layer was filtered, and DMAC (100 ml) was added tothe filtrate and concentrated under vacuum. Product assay: 21.86 g,quantitative yield.

1.9 Tert-Butylamide Formation

Indazole-7-carboxylic acid 10 (50.3 g, 295 mmol) was dissolved in DMF,and added CDI (59.1 g, 354 mmol) at RT. After 1.5 hr, tert-butylamine(62.5 ml, 589 mmol) was added to the reaction mixture. The resultingreaction mixture was warmed to 40° C. until complete conversion, thencooled to RT. Water (600 ml) was added dropwise causing the mixture toform a thick slurry. Solid was collected by filtration and washed with10% DMF in water (250 ml) followed by water. The solid was dried undervacuum. Beige solid: 55.31 g, 86% isolated yield.

1.10 Carbon-Nitrogen Coupling

A mixture of the protected piperidine 9 (113 g, 18.23 wt %, 60.6 mmol)in DMAc (160 mL), compound 11 (13.82 g, 63.6 mmol), and K₂CO₃ (25.6 g,182 mmol) was degassed by bubbling nitrogen. To the mixture was addedCuBr (0.444 g, 3.03 mmol) and 8-hydroxyquinoline 12 (0.889 g, 6.06mmol), and the resulting mixture was warmed to 110° C. until completeconversion. The reaction mixture was then cooled, filtered through a padof Celite, and rinsed with DMAc (100 ml). The filtrate was warmed to 35°C. and added citric acid aqueous solution (10%) dropwise to form a lightgreen slurry. After cooled to room temperature, the slurry was filtered,and the cake was washed with DMAc/Water (2/1, 150 ml) followed bycopious amount of water. The solid was dried under vacuum with nitrogen.Net weight: 27.24 g. LC assay: 26.77 g, 98.3 wt %. Assay yield: 93.6%.

1.11 Double Deprotection

To compound 13 (20.0 g, 41.2 mmol) was added MSA (60 ml) and o-xylene(40 ml), and the the reaction mixture was warmed to 40° C. until thecomplete conversion judged by HPLC. The reaction mixture was cooled toRT and added water (140 ml) slowly maintaining the temperature<25° C.When the water addition was completed, the organic layer was removed,and the aq. layer was washed with toluene. The aqueous layer wasfiltered through a glass funnel, and the filtrate was added an aqueoussolution of TsOH (11.77 g in 23.5 ml) slowly at RT causing a thickslurry to form. Solid was collected by filtration, washed with water,and dried under vacuum. The titled compound was obtained as a whitepowder. Net weight: 20.6 g. LC assay: 20.0 g, 97.3 wt %. Assay yield:95.2%.

Example 2

The following Example 2 describes synthesis of thetrifluoromethylacetate salt of compound2-{4-[(3S)-Piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide:

2.1 Cumylamide Formation

To the indazole-7-carboxylic acid 10 (400 mg, 2.47 mmol) intetrahydrofuran (9.9 mL), was sequentially added HATU (1.13 g, 2.96mmol), DIPEA (2.15 mL, 12.3 mmol), and cumylamine (500 mg, 3.70 mmol) at50° C. The reaction was stirred overnight before being concentrated andloaded directly onto a silica column, eluting with 10-30% EtOAc/hexane.The product was collected and concentrated to afford the desired productas a colorless solid (557 mg, 81% yield).

2.2 Carbon-Nitrogen Coupling

A sealed vial containing the indazole-7-carboxamide 15 (50 mg, 0.18mmol), copper(I) iodide (2.6 mg, 0.014 mmol), potassium phosphatetribasic (80 mg, 0.38 mmol), and aryl bromide 9 (73.1 mg, 0.215 mmol)was evacuated and backfilled with argon (×3).Trans-N,N′-dimethylcyclohexane-1,2-diamine (11.3 μL, 0.072 mmol), andtoluene (179 μl) were then added successively and the sealed vial washeated at 110° C. overnight. The vial was then cooled and toluene (0.30mL) was added to the slurry. Crude LC/MS indicated>20:1 selectivity forthe desired indazole isomer. The crude product was purified by loadingdirectly onto a Biotage Snap 10G silica column, eluting with 5-50%EtOAc/hexane. The product was collected and concentrated to afford thedesired product as a colorless solid (78 mg, 81% yield).

2.3 Double Deprotection

To the piperidine-1-carboxylate 16 (45 mg, 0.084 mmol), was addedtriethylsilane (267 μL, 1.67 mmol) and TFA (0.965 mL, 12.5 mmol) at 25°C. The reaction was stirred for 4 hours and the reaction wasconcentrated in vacuo, and purified by mass triggered reverse phase HPLC(acetonitrile:water, with 0.1% TFA modifier). Lyphilization gave thedesired product as the TFA salt and as a white solid (31 mg, 85% yield).HRMS (ESI) calc'd for C₁₉H₂₁N₄O [M+H]⁺: 321.1710, found 321.1710.

Example 3

Following the conditions used in sections 2.1 and 2.2 of Example 2, thisExample 3 shows regioselective N2 arylation of compound 9 using variousamide protecting groups. The indazole-7-carboxylic acid 10 was reactedwith various amines to generate a protected amide. The amide protectinggroups are indicated by the R group in Table 2. The amide coupling yieldis provided in Table 2. The Cu-mediated carbon-nitrogen coupling of thisindazole to compound 9 was then tested to determine if regioselective N2arylation was possible. The arylation yield is also provided in Table 2.The data shows that various amide protecting groups on the indazoleintermediate are suitable to generate efficient regioselective N2arylation of compound 9.

TABLE 2 Amide Cu-Mediated R coupling yield Arylation yield

52% 96%

80% 88%

88% 94%

89% 97%

What is claimed is:
 1. A compound of formula IV:

wherein:

R¹ is C₄₋₈ alkyl, C₃₋₁₀ cycloalkyl, C₄₋₁₀ heterocyclyl, aryl, orheteroaryl; and R² is an amine protecting group.
 2. The compound ofclaim 1, wherein R¹ is t-butyl, cumyl, or trityl.
 3. The compound ofclaim 1, wherein the amine protecting group is selected from the groupconsisting of formyl, acetyl, trifluoroacetyl, benzyl, benzoyl,carbamate, benzyloxycarbonyl, p-methoxybenzyl carbonyl,tert-butoxycarbonyl, trimethylsilyl, 2-trimethylsilyl-ethanesulfonyl,trityl, substituted trityl groups, allyloxycarbonyl,9-fluorenylmethyloxycarbonyl, nitro-veratryloxycarbonyl,p-methoxybenzyl, and tosyl.
 4. The compound of claim 1, wherein theamine protecting group is tert-butoxycarbonyl.
 5. The compound of claim2, wherein the amine protecting group is selected from the groupconsisting of formyl, acetyl, trifluoroacetyl, benzyl, benzoyl,carbamate, benzyloxycarbonyl, p-methoxybenzyl carbonyl,tert-butoxycarbonyl, trimethylsilyl, 2-trimethylsilyl-ethanesulfonyl,trityl, substituted trityl groups, allyloxycarbonyl,9-fluorenylmethyloxycarbonyl, nitro-veratryloxycarbonyl,p-methoxybenzyl, and tosyl.
 6. The compound of claim 2, wherein theamine protecting group is tert-butoxycarbonyl.
 7. The compound of claim1, wherein R¹ is t-butyl and R² is tert-butoxycarbonyl, which is(S)-tert-butyl 3-(4-(7-(tert-butylcarbamoyl)-2H-indazol-2-yl)phenyl)piperidine-1-carboxylate:


8. The compound of claim 1, wherein R¹ is cumyl and R² istert-butoxycarbonyl, which is (S)-tert-butyl 3-(4-(7-((2-phenylpropan-2-yl)carbmoyl)-2H-indazol-2-yl)phenyl)piperidine-1-carboxyl ate: